@article{DE_1999_35_1_a10,
     author = {I. T. Kiguradze and T. Kusano},
     title = {On periodic solutions of higher-order nonautonomous ordinary differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {72--78},
     publisher = {mathdoc},
     volume = {35},
     number = {1},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1999_35_1_a10/}
}